Telomerase Specific Caspase Transfer for Gliomas

描述（由申请人提供）：我们治疗恶性胶质瘤的努力是 专注于将caspase基因转移到肿瘤中的方法。因为 细胞凋亡途径可能在肿瘤中被破坏，半胱天冬酶是肿瘤的支柱。 凋亡程序，这种方法是最有前途的策略之一， 癌症基因治疗然而，如果半胱天冬酶被转导到正常大脑， 细胞会发生凋亡。将细胞凋亡诱导局限于肿瘤 细胞，我们需要建立一个肿瘤特异性表达系统的半胱天冬酶。 端粒酶是肿瘤靶向系统的一个特别有吸引力的靶点。 这是因为绝大多数恶性胶质瘤都有端粒酶活性， 而大多数正常的脑细胞则没有。端粒酶的激活与 在端粒酶催化亚单位的转录水平上受到调控 （hTERT）。因此，我们假设通过使用hTERT启动子驱动的 载体系统中，半胱天冬酶的表达可限于 端粒酶阳性恶性胶质瘤。在初步研究中，我们构建了 半胱天冬酶-8（起始半胱天冬酶）或rev-caspase-6（执行半胱天冬酶） 具有hTERT启动子的表达载体（hTERT/caspase-8或rev-caspase-6） 并证明每种构建体均诱导端粒酶阳性细胞凋亡， 恶性胶质瘤细胞，而不是在培养的星形胶质细胞缺乏端粒酶。 此外，裸鼠皮下肿瘤的生长显著低于对照组， 通过用hTERT/rev-caspase-6处理抑制。另夕h hTERT/caspase-8或rev-caspase-6的抗肿瘤作用被增强， 与抗癌药顺铂联合使用。本提案的目的是 研究是否用hTERT/caspase-8或rev-caspase-6治疗 构建体是治疗端粒酶阳性恶性胶质瘤的有效方法 使用人类恶性神经胶质瘤的实验模型。具体目标是： 1)选择用于hTERT/caspase-8体内治疗的肿瘤模型系统 或rev-胱天蛋白酶-6构建体的抗肿瘤作用，2）研究 hTERT/caspase-8或rev-caspase-6构建体对颅内肿瘤的作用，3） 研究它们体外和体内抗肿瘤功效， 常规治疗（顺铂、替莫唑胺或γ-照射），以及4） 研究的分子机制的影响， hTERT/半胱天冬酶-8或rev-半胱天冬酶-6。这项工作的一个独特的重点是强调 关于半胱天冬酶的端粒酶特异性基因转移。我们预计 在目前的建议中描述的研究将导致一个新的和有前途的 端粒酶活性表达的恶性胶质瘤的靶向治疗方法。

DESCRIPTION (provided by applicant): Our efforts to treat malignant gliomas are focused on methods to transfer the caspase genes to tumors. Because the apoptotic pathway may be disrupted in tumors and caspases are the mainstay of apoptosis programs, this approach is one of the most promising strategies for cancer gene therapy. However, if caspases were transduced to normal brain cells, they will undergo apoptosis. To restrict induction of apoptosis to tumor cells, we need to establish a tumor specific expression system of caspases. Telomerase is a particularly attractive target for the tumor-targeting system. It is because a vast majority of malignant gliomas have telomerase activity, while most normal brain cells do not. Activation of telomerase is tightly regulated at the transcriptional level of the telomerase catalytic subunit (hTERT). Therefore, we hypothesize that by using the hTERT promoter-driven vector system, the expression of caspases can be restricted to telomerase-positive malignant gliomas. In preliminary studies, we constructed the caspase-8 (initiator caspase) or rev-caspase-6 (executioner caspase) expression vector with the hTERT promoter (hTERT/caspase-8 or rev-caspase-6) and demonstrated that each construct induced apoptosis in telomerase-positive malignant glioma cells, but not in cultured astrocytes lacking telomerase. Furthermore, the growth of subcutaneous tumors in nude mice was significantly suppressed by the treatment with the hTERT/rev-caspase-6. Additionally, the antitumor effect of hTERT/caspase-8 or rev-caspase-6 was enhanced by the combination with anticancer drug, cisplatin. The goal of this proposal is to investigate whether treatment with the hTERT/caspase-8 or rev-caspase-6 construct is an effective approach for telomerase-positive malignant gliomas using an experimental model of human malignant gliomas. The specific aims are: 1) to select tumor model systems for the in vivo treatment with hTERT/caspase-8 or rev-caspase-6 construct, 2) to investigate the antitumor effect of the hTERT/caspase-8 or rev-caspase-6 construct on intracranial tumors, 3) to investigate their in vitro and in vivo antitumor efficacy combined with conventional therapy (cisplatin, temozolomide, or gamma-irradiation), and 4) to investigate the molecular mechanisms underlying the effect of the hTERT/caspase-8 or rev-caspase-6. A unique focus of this work is the emphasis on the telomerase-specific gene transfer of caspases. We anticipate that the studies described in the current proposal will lead to a novel and promising targeting approach for malignant gliomas expressing telomerase activity.